RNA sequencing analysis uncovers the role of aldehyde oxidase TcAOX2 in regulating toxic substance susceptibility in the red flour beetle, Tribolium castaneum

Aldehyde oxidase (AOX) is a class of metabolic enzymes, which can make T. castaneum resistant to aldehyde insecticides and thus increase the difficulty of control. In this study, we first examined the killing effect of benzaldehyde, one of the main active components of mugwort essential oil, to T. castaneum and demonstrated the involvement of TcAOX2 in regulating the sensitivity of T. castaneum to benzaldehyde. Subsequently, we identified a total of 105 differentially expressed genes relative to controls by RNA sequencing (RNA-Seq) analysis of T. castaneum late larvae injected with dsTcAOX2, including 67 up-regulated and 38 down-regulated expressed genes. Analysis and functional annotation of differentially expressed genes using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The results showed that the expression of apolipoprotein D, carboxypeptidase A, serine protease P40, pancreatic triacylglycerol lipase, and other genes related to immunity and metabolism, their expression also decreased with the decrease of TcAOX2 expression. The down-regulation of the expression of these genes may make T. castaneum less immune and less able to cope with stressful environments. This suggests that changes in TcAOX2 gene expression may affect the expression of these metabolism- or immunity-related genes, which in turn affects T. castaneum sensitivity to external toxicants. In conclusion, our results provide a theoretical basis for exploring the detoxification mechanism of aldehyde oxidase in T. castaneum and for screening target genes in response to external stimuli.